The Napster software connects you with a virtual community where you can trade MP3 files with other users transferring files directly from their hard drive to yours. And you don't have to worry about security because Napster recognizes only MP3 files. As far as we know, there's no way for other Napster users to look inside your computer and grab other types of files.
There are many reasons Napster has spread like dandelions, not the least of which is that it's very easy to use. Then there's also the matter of scoring free music downloads encoded in the MP3 file format, but let's focus on Napster's simplicity. Download the software, install it, press Connect and you're ready to start searching. If you want to share the MP3 files on your hard drive with others, you can. But if you don't, that's OK, too.